Home Environment Encyclopedia of Cultivated Plants: From Acacia to Zinnia
One scientist judges carrot (Daucus carota) the “most important of all the root crops.” Tropical varieties of carrot are annual whereas temperate cultivars are biennial, though they are grown as annuals. A biennial carrot fills its taproot in the first year and flowers in the second. The largest portion of a carrot is the edible taproot. In the Umbelliferae or Parsley family, carrot is known a keroton in Greek. One cup of carrots has 20,000 international units of beta-carotene, the precursor of vitamin A, four times the recommended daily allowance. The University of Wisconsin has bred carrots with three to five times the beta-carotene of other varieties with the aim of planting these new cultivars in the developing world where vitamin A deficiency is acute. Among its benefits, 18th-century religious reformer John Wesley thought carrot cured asthma.
According to one scientist, the carrot is a variant of the Eurasian flower Queen Anne’s lace. It originated in the Himalayan and Hindakush Mountains of Asia and was domesticated in Afghanistan, Russia, Iran, Pakistan, and Turkey. Wild specimens may still be found in southwestern Asia, the Mediterranean Basin, Africa, Australia, and the Americas. Humans first cultivated carrot 2,000 to 3,000 years ago. Archaeologists have found carrot seeds in Switzerland dating to this period. From Afghanistan, carrot migrated to the Mediterranean Basin. By 500 BCE, the Greeks cultivated the root, using carrot juice to treat stomachache. In antiquity, farmers and gardeners grew purple, yellow, or white carrots. The orange carrot would be a latecomer. Arabs may have brought carrot from Afghanistan to Northern and Western Europe. In the ninth century, Frankish king Charlemagne may have known of the carrot, though according to one authority carrot was not introduced into Europe until the 11th through the 14th centuries and into China, India, and Japan between the 14th and 17th centuries. By one account, the Flemish introduced carrot into England in 1558. The orange carrot arose as a sport in the Netherlands in the 17th century. Its superior flavor led to its adoption throughout Europe. In the 18th century, English queen Anne and her friends admired carrots in the royal garden. The queen challenged them to make lace as delicate and beautiful as carrot flowers. The queen’s lace was judged the best, and thereafter the carrot flower was known as Queen Anne’s lace.
In the 16th century, the Spanish introduced the carrot into the Americas, planting it on the island of Margarita near Venezuela. In either 1609 or 1610, the English may have introduced the carrot into Jamestown, Virginia. Another account holds that the American colonists did not grow carrot until about 1620 and then in Salem, Massachusetts. In the early 17th century, the Dutch derived the cultivar Hoorn, named after Hoorn, the Netherlands. A popular cultivar, Europeans brought it to the American colonies, where it was known as Early Dutch Hoorn. In 1870, Americans planted Danvers, a cultivar named for Danvers, Massachusetts. The variety Nantes originated in Nantes, France.
In 2006, China was the leading producer of carrots. The Chinese interplant carrot with other crops. They add carrots to recipes as a source of color, though they find the root flavorless. The United States ranked third, trailing China and Russia. California produces 80 percent of U.S. carrots. Florida, Michigan, and Washington are also important producers. Americans add carrot to beef or vegetable stew, spaghetti sauce, and minestrone. The carrot is ubiquitous in salad. The French slice carrots, cooking them in chicken broth with parsley and tarragon. The Turks combine carrot with ginger and sour cream, a dish known as carrot plaki. The Poles add cream and dill to carrots. Germans make carrot nut bread, from which Americans derive carrot cake.
Carrots have more sugar than any other vegetable except beets. Farmers and gardeners grow carrots for fresh consumption or processing. The carrot may be black, red, yellow, or orange. The essential oils extracted from the roots kill bacteria. The essential oils from the seeds are used to treat kidney ailments and dropsy. The carrot may be planted as soon as the temperature reaches 45°F, though seeds will not germinate until the temperature is at least 68°F. Seeds will not germinate above 80°F according to one gardener or above 86°F according to another. Seeds germinate in 6 to 21 days. Because carrot does not transplant well, it is best planted where the gardener intends to grow it. Some gardeners sow carrot and radish. Radish germinates quickly, marking the spot where carrot will later germinate. Radish roots keep the soil loose for the enlarging carrot taproot. Alternatively, one may plant carrot with bok choy. In 30 to 45 days, the gardener may harvest bok choy, opening space in the garden for young carrots. For a continuous harvest, one may plant new seeds after harvesting half the crop. The carrot reaches the peak of flavor when planted in early spring, though carrot may be planted in late summer for an autumn harvest. Seeds may be planted three-quarters of an inch deep and four inches apart. Carrot grows best between 60°F and 80°F, the tops reaching a height of three-and-a-half to seven-and-a-half inches. The soil should be cultivated deeply and should be loose to allow carrot to enlarge its taproot unimpeded. The soil should drain well to prevent it from harboring fungi. Where the soil is heavy, the gardener may plant varieties with a short taproot. One gardener recommends the application of a balanced fertilizer to the soil. Carrot benefits from the addition of organic matter to the soil. The gardener may add wood ashes to the soil as a source of potassium and to sweeten the flavor of carrot. Carrots may be harvested when they are young for maximum flavor and nutrition. The gardener may leave carrots in the ground, harvesting only as much as she needs for a meal. After a severe frost, all carrots should be picked and stored in a cool, humid place. The tops should be removed.
Science and Breeding
Current cultivars are genetically uniform because they derive from only a few 18th-century Dutch varieties. With the aim of increasing the genetic diversity of current varieties, Russia’s Vavilov Institute, named for 20th-century Russian agronomist Nikolai Vavilov, has amassed a collection of more than 1,000 culti- vars. The U.S. Department of Agriculture’s North Central Regional Plant Introduction Station in Ames, Iowa, has amassed a collection of 800 cultivars. The United Kingdom, France, the Netherlands, and Japan also maintain collections. Worldwide gene banks hold some 5,600 varieties. Breeders aim to derive culti- vars with early-maturation, high-yield, high-beta-carotene content; the ability to set seeds under poor conditions; uniform root size, shape, and color; small tops; tender roots; improved flavor, texture, sugar content, and dry matter; resistance to cracking and breaking during the harvest; roots that taper uniformly; slowness to bolt; tolerance of poor soil and climate; wide adaptability; and resistance to diseases, especially leaf blight, black rot, powdery mildew, bacterial soft rot, and carrot yellows, and to pests including caterpillars and the carrot fly.
Bearing perfect flowers and male flowers, a carrot may have more than 1,000 flowers. The outer flowers mature first, though flowers in the core have the most fertile pollen. Each flower has five sepals, five petals, five stamens, and two carpels. Each carpel has two ovules. Because the pollen and ova of a single perfect flower are fertile at different times, the carrot is not normally a self-pollinator. In 1937, scientists made the first hybrid cross of two inbred lines of carrot. Because carrot is, with the aid of insects, a cross-pollinating plant, the production of inbreds reduces the number of seeds. A hybrid yields a taproot three times more massive than the root of either parent. Hybrids have more beta-carotene than the parents. The degree of heterosis, hybrid vigor, is 20-22 percent higher when one parent in the cross is male sterile than when neither parent is male sterile. Male sterility is of two types. In the first, the anthers shrivel before anthesis and so do not shed pollen. In the second case, a flower does not produce anthers. The second type of sterility is more commonly used in breeding programs. Male sterile plants are therefore useful only as the female in a hybrid cross. In 1953, scientists discovered the first male sterile carrot near Orleans, Massachusetts, naming it the Cornell cytoplasm. The Cornell cytoplasm has been used to produce the majority of U.S. hybrids. Hybrids are three-way crosses. First, the breeder crosses two inbred lines to yield hybrid progeny. Second, these progeny are crossed with another line, presumably a cultivar rather than another inbred, to yield a second- generation hybrid. In the production of a hybrid, the breeder discards progeny with undesirable characteristics, for example bolting, poor color, or irregular length or shape of the taproot.
Hughes, Meredith Sayles, and Tom Hughes. Buried Treasure: Roots and Tubers. Minneapolis: Lerner, 1998.
McGee, Rose Marie Nichols, and Maggie Stuckey. The Bountiful Container: A Container Garden of Vegetables, Herbs, Fruits, and Edible Flowers. New York: Workman, 2002.
Singh, P. K., S. K. Dasgupta, and S. K. Tripathi, eds. Hybrid Vegetable Development. Binghamton, NY: Food Products Press, 2004.
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